Overall objectives PRIMARY: - Assessment of early changes in DCE-MRI and ultrasound measures of tumor perfusion in the setting of pazopanib therapy for patients with metastatic clear cell renal cell carcinoma SECONDARY: - Correlation of baseline DCE-MRI and ultrasound parameters and clinical outcome - Correlation of early (48 +/- 24 hr after treatment) changes in DCE-MRI and ultrasound parameters and clinical outcome - Correlation of baseline (and changes) in DCE-MRI and ultrasound parameters with VHL status in tumors and histocytometric analysis of endothelial cell activation in archival nephrectomy specimens - Provide an insight in the respective predictive values of DCE-MRI and US for pazopanib treatment